I found the thread that i had read. It was posted by"applepoop 2008" it says:
phosphoric acid on the other hand is superior in every way except being a ph of .87 at 85% food grade vs sulfurics .3 ph at 97%:
1. non carcinogenic
2. sourced from food grade phosphoric acid
3. weaker than sulfuric thus much safer to handle
4. sold readily on amazon for 48$ a gallon or less
onto the tutorial.
what you need:
1. safety glasses
2. rubber gloves
3. measuring glass at least 32 oz
4. 1 gallon food grade phosphoric acid
https://www.amazon.com/Gallon-Grade-Phosphoric-Remover-Clean/dp/B06XZSW3QX/ref=sr_1_9?ie=UTF8&qid=1496911965&sr=8-9&keywords=acid+food+grade
5. 4 1 gallon containers of distilled water
6. dust mask
first put on gloves and glasses, open all 4 gallons of distilled water
pour out 32 oz into measuring glass from each bottle, discarding or saving for later
pour 32 oz of phosphoric acid into DRY measuring glass and then pour 32 oz into each gallon jug of water( we pour acid into water because acid will react violently if we do the opposite)
this makes each gallon contain 21% phosphoric acid, gh ph down has a concentration of 10-30% phosophoric acid putting each gallon of solution right in the middle of their "trade secret"